Pathogen recognition by plants results in the activation of signaling pathways that induce defense reactions. There is growing evidence indicating that epigenetic mechanisms directly participate in plant immune memory. Here, we discuss current knowledge of diverse epigenomic processes and elements, such as noncoding RNAs, DNA and RNA methylation, histone post-translational modifications, and chromatin remodeling, that have been associated with the regulation of immune responses in plants. Furthermore, we discuss the currently limited evidence of transgenerational inheritance of pathogen-induced defense priming, together with its potentials, challenges, and limitations for crop improvement and biotechnological applications. To defend against microbial pathogens, plants have developed a sophisticated immune system. Upon recognition of external microbe-associated molecular patterns (MAMPs) or internal microbial effectors that are delivered into the host cells, signal transduction events are triggered, leading to rapid defense responses that include massive transcriptional reprogramming. These events are followed by the systemic activation of defense programs at distant, nonchallenged sites, a process termed ‘systemic acquired resistance’ (SAR) and linked to priming, whereby plants memorize previous attacks and can respond more robustly to subsequent pathogen challenges. Recent evidence demonstrates that plant defense gene expression also involves epigenetic mechanisms, such as DNA methylation and histone modifications, that are closely linked to the dynamical chromatin states.